Today BMJ STI honours World Human T-cell Leukaemia Virus (HTLV) Day. More than 40 years ago, before the discovery of HIV, Bob Gallo and his team discovered HTLV-1, an oncovirus and the first recognised human retrovirus. An estimated 5-10 million individuals have been exposed to infection with HTLV type-1 globally, with specific hyperendemic regions (1). However, the true prevalence of HTLV is likely to be higher due to substantial underdiagnosis and a lack of systematic epidemiological studies. HTLV is predominantly transmitted through cell-containing bodily fluids including blood, semen, genital secretions and breast milk. Risk factors include unprotected sex, injecting drug use, and receiving unscreened blood, blood products or transplantation.
Over a lifetime, about 5% of people living with HTLV-1 develop a form of blood cancer known as adult T-cell leukaemia/lymphoma (ATL) and up to 3% develop chronic inflammation of the spinal cord known as HTLV-1 associated myelopathy or tropical spastic paraparesis (HAM/TSP) which causes disability. Many other inflammatory conditions (e.g. affecting the skin, eyes, joints or respiratory tract) have also been associated with HTLV-1 infection.
HTLV is a neglected virus with no cure, specific antiviral treatment or vaccine. In most countries, there is no public health effort to test key populations and no clear provision of referral pathways. In 2021 the World Health Organization (WHO) acknowledged HTLV as a health risk, promising to raise awareness and provide advice on public health prevention measures.
In this episode of BMJ STI Podcast, Ms Kristy Blakeborough, a patient advocate based in the UK, Prof Yoshihisa Yamano, a neurologist who specialises in HAM/TSP in Japan, and Assoc Prof Keith Chappell, a researcher who has been working on developing an HTLV vaccine in Australia, join Dr. Fabiola Martin, HTLV specialist and President of the International Retrovirology Association (IRVA), to discuss patients’ perspectives, clinical trials for HAM/TSP and HTLV vaccines development. Join us for this special episode of the STI BMJ Podcast!
Facts and Highlights
- HTLV-1 can be transmitted through condomless sex, blood products and transplantation, sharing used needles and from mother-to-child, predominantly through prolonged breastfeeding.
- Due to the predominately asymptomatic nature of HTLV-1, it is often transmitted unknowingly.
- People burdened with HLTV-1 are often diagnosed through routine screenings at national blood donation services
- HTLV-1 primarily targets human CD4+ T-lymphocytes, by integrating its DNA into the human genome indefinitely.
- 95% of people burdened with HTLV-1 do not develop specific diseases.
- Clinical research output has been limited due to limited awareness and lack of funding. For years it was assumed that clinical trials for HAM/TSP would not be feasible. The HAMLET-P trial showed for the first time that it is possible to conduct randomised and double-blind trials in people with HAM/STP.
- Whereas we do not yet have a vaccine for HTLV-1, the success of novel vaccine development strategies for SARS-CoV-2 raise hopes for both preventative and therapeutic HTLV-1 vaccines.
What is urgently needed for HTLV-1
- A proactive engagement of the WHO with HTLV-1 experts to set up the WHO HTLV Health Topic webpage.
- National and international interventions to identify at-risk populations, reduce transmission, improve diagnosis, reduce stigma and improve access to health care for people living with HTLV-1.
- Development of pathways for HTLV-1 testing, including routine STI screening for key populations, provision of counselling for those with HLTV-1 and for those at risk of infection, and implementation of specialist referral pathways.
Further reading and resources